1. Field of the Invention
The present invention is related to vacuum sweeping vehicles for collecting debris from streets and parking lots, and more particularly to such vehicles which are lightweight.
2. Description of the Prior Art
For a number of years, street sweepers and the like have been used to maintain the cleanliness of expansive paved spaces. Typically, street sweepers are mounted on a heavy duty truck or vehicle having a water storage tank, rotatable brushes, vacuum system driven by a separate engine, and a large hopper in which swept up debris is collected. Typically, intricate heavy duty hydraulic systems and mechanisms are incorporated for dumping the hopper, extending and retracting brushes, and the like. Because of the collective weight of all of these systems and components, heavy duty large trucks or vehicles are employed to provide the required capacity to carry the weight of the mechanism and any trash collected in the hopper. Experience has proven that, not only are such sweepers large, bulky, costly to manufacture, fuel inefficient, and possess limited maneuverability, but have restricted capacity because of typical governmental weight restrictions imposed on the road over which such vehicles operate in the collection and disposal of trash.
Consequently, in some instances, the industry adopted the use of less sophisticated vacuum trucks, usually incorporating fewer peripheral components sometimes limited to a vacuum suction head for sucking debris into a vacuum system driven by a separate drive engine to collect debris into a smaller debris collection hopper. These less sophisticated systems, being more cost effective and lighter for mounting on a truck with a smaller wheel base and thus more maneuverable; however may constitute a compromise in performance.
These newer generation vacuum trucks, while having gained a certain degree of commercial success, continue to share certain shortcomings with the traditional heavier sweepers. They typically incorporate a debris hopper constructed of thick, 12 gauge steel to withstand the pressure differential generated by the vacuum acting on the interior of the hopper when in operation. Even with smaller hoppers, the weight thereof may be on the order of 1,600 lbs. thus requiring a vehicle with a rear axle load capacity on the order of one ton. Such vehicles may be of considerable size, relatively expensive to procure and suffer from fuel inefficiency.
The manufacture of a steel hopper of this type typically involves cutting steel to size to define the walls of the hopper. The walls are erected and the adjacent edges welded together to form a generally box-shaped hopper having pronounced oblique angled junctions. In operation, the hopper is subjected to vacuum induced air flow. Such box-shaped hopper construction provides a relatively inefficient flow path often producing stagnation flow areas near the oblique junctions of the hopper walls and tending to cause eddies and turbulent air flow patterns within the hopper. Such air flow characteristics can provide resistance to uniform air flow and cause debris to churn within the hopper rather than collecting in an efficient manner along the bottom wall. Moreover, these air flow characteristics decrease vacuum efficiency, serving to detract from the efficiency of the sweeping process and add to the capacity required for the vacuum system. In addition, it has been found that such steel hoppers, when operating in the normal atmosphere, will deteriorate and rust through at the welded seams and through the side walls, thus requiring extended maintenance, repair and replacement.
Hence, those skilled in the art have been desirous of a vacuum truck having a less bulky, lighter weight hopper that may be mounted on a standard light duty truck chassis to improve vehicle fuel efficiency, minimize vehicle wear and tear, and reduce overall cost. The hopper should be constructed to minimize stagnant and turbulent flow patterns under operating vacuum and air flow conditions for enhanced vacuum efficiency. In addition, the hopper should offer a construction not prone to corrosion. Furthermore, it is desirable that the hopper incorporate a minimum number of components to facilitate ease of assembly, in turn, lowering manufacturing costs. The present invention meets these needs and others.